Asymmetric synthesis cyclopropanation, rhodium catalyst

This collection begins with a series of three procedures illustrating important new methods for preparation of enantiomerically pure substances via asymmetric catalysis. The preparation of 3-[(1S)-1,2-DIHYDROXYETHYL]-1,5-DIHYDRO-3H-2.4-BENZODIOXEPINE describes, in detail, the use of dihydroquinidine 9-0-(9 -phenanthryl) ether as a chiral ligand in the asymmetric dihydroxylation reaction which is broadly applicable for the preparation of chiral dlols from monosubstituted olefins. The product, an acetal of (S)-glyceralcfehyde, is itself a potentially valuable synthetic intermediate. The assembly of a chiral rhodium catalyst from methyl 2-pyrrolidone 5(R)-carboxylate and its use in the intramolecular asymmetric cyclopropanation of an allyl diazoacetate is illustrated in the preparation of (1R.5S)-()-6,6-DIMETHYL-3-OXABICYCLO[3.1. OJHEXAN-2-ONE. Another important general method for asymmetric synthesis involves the desymmetrization of bifunctional meso compounds as is described for the enantioselective enzymatic hydrolysis of cis-3,5-diacetoxycyclopentene to (1R,4S)-(+)-4-HYDROXY-2-CYCLOPENTENYL ACETATE. This intermediate is especially valuable as a precursor of both antipodes (4R) (+)- and (4S)-(-)-tert-BUTYLDIMETHYLSILOXY-2-CYCLOPENTEN-1-ONE, important intermediates in the synthesis of enantiomerically pure prostanoid derivatives and other classes of natural substances, whose preparation is detailed in accompanying procedures. 

Numerous other examples of asymmetric intramolecular cyclopropanations with chirally mod-ified rhodium catalysts have been reported 116 125. Asymmetric eyclopropanation of 1,3-di-enes leads to chiral vinyl cyclopropanes and products derived thereof126,127. Asymmetric eyclopropanation is also used in the synthesis of chiral cyclopropanes starting from unsymmet-rically substituted alkynes128. Polymer-supported rhodium catalysts of this type can be recov-... 

The cyclopropane ring is a common structural motif found in pyrethriods, the antidepressant tranylcyclopromine, papin and cystein protease inhibitors, potential antipsychotic agents, and anti-HIV compounds. Thus, considerable attention has been paid to the stereoselective synthesis of cyclopropane-containing compounds. The use of rhodium in cyclopropanation was made popular by contributions from Doyle and Davies. They have focused, over the years, on using chiral Rh(II) catalysts for asymmetric cyclopropanation via the decomposition of diazo compounds in the presence of olefins. Examples of the Rh(II)-... 

Synthesis of the chiral catalysts to introduce enantioselectivity in carbene transfer reactions is a subject of great interest. Often copper and rhodium chiral catalysts are of choice for the carbene transfer reactions. In some reports, immobilized chiral dirhodium (II) catalyst were employed successfully in asymmetric cyclopropanation reactions. Ubeda and coworkers reported the immobilization of chiral Rh2(02CR)2(PC)2 (PC = ort/io-metalated phosphine) compounds on cross-linked polystyrene (PS) resin by an... 

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